Conventional water dispersible granules are produced by mixing and grinding agricultural chemical technical products, and wetting agents, dispersants, and fillers. However, these water dispersible granules have problems. For example, the water dispersible granules have a small apparent specific gravity and increased volume, because the water dispersible granules contain finely pulverized powders of the agricultural chemical technical products and inorganic minerals, and the water dispersible granules are not preferable for maintaining health of workers, because the fine powders become dusty when suspending the fine powders in water to prepare spray solution, and, they require much time to be measured, because they are fine powders, and so various attempts have been recently made to develop water dispersible granules in which the water dispersible granules are granulated.
Water dispersible granules are produced by mixing, grinding and granulating agricultural chemical technical products, wetting agents, dispersants, binders, and other inert ingredients, as needed. Because the water dispersible granules are required to disintegrate and disperse immediately after being put into water, various contrivances have been attempted to enable the granules to disintegrate and disperse. Methods of producing agricultural and horticultural water dispersible granules have been reported, by which, for example, formaldehyde condensate of alkylnaphthalene sulfonates, lignosulfonates, polyacrylates, alkylaryl sulfonates, polycarboxylates, polyoxyethylene polyoxypropylene block polymers, polystyrene polyoxyethylene block polymers, or the like, are used as a dispersant, and sodium alkylnaphthalenesulfonates, sodium alkylsulfates, sodium alkylbenzenesulfonates, sodium alkylsulfosuccinates, polyoxyethylene alkylarylethers, or the like, are used as a wetting agent (for example, Non-patent Document 1).
In regard to methods of producing agricultural and horticultural water dispersible granules using agricultural chemical technical products liquid at room temperature or having a low melting point, which are difficult to produce, formulation methods have been proposed in which the agricultural chemical technical products liquid at room temperature or having a low melting point are mixed with a great deal of inactive material, or in which the agricultural chemical technical products are dissolved in a solvent to be adsorbed by adsorbent carriers (for example, Non-patent Document 1).
However, even when these methods are used, it is difficult to produce water dispersible granules having good disintegrability and dispersibility in water by using agricultural chemical technical products having a melting or softening point of 70° C. or below, although the cause is unknown. Therefore, a method of producing water dispersible granules by, for example, mixing agricultural chemical technical products having a melting point of 70° C. or below with calcined silica produced by wet process and dispersants has been proposed as an improved method of producing water dispersible granules (see, for example, Patent Document 1).
However, according to this method, water dispersible granules having sufficient disintegrability and dispersibility cannot be produced when using agricultural chemical technical products of which the melting or softening point is 70° C. or below.
Non-patent Document 1: Pesticide Science Society of Japan, Pesticide Formulation Guide, edited by Japan Agricultural Formulation and Application Symposium, issued by the Japan Plant Protection Association, Oct., 30th, 1997, p. 22 to 24.
Patent Document 1: Japanese Patent Application, First Publication No. Hei 3-163006